1. Field of the Invention
This invention relates to a circuit interrupter and more particularly to an interrupter of the vacuum type which includes an evacuated envelope, in which a movable and a stationary contact rod are arranged to open and close a circuit.
2. Description of the Prior Art
In a vacuum circuit interrupter of the prior art, a pair of contacts able to engage each other are housed in an evacuated envelope composed of an appropriate combination of insulating and metallic members, the former being made of glass or ceramics and the latter being made of an iron-nickel or iron-nickel-cobalt alloy having a coefficient of thermal expansion which closely matches that of the glass or ceramics. However, iron-nickel or iron-nickel-cobalt alloys are relatively expensive.